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    SubjectRe: [PATCH v2 02/18] x86/resctrl: Access per-rmid structures by index
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    Hi James,

    On 1/13/2023 9:54 AM, James Morse wrote:
    > Because of the differences between Intel RDT/AMD QoS and Arm's MPAM
    > monitors, RMID values on arm64 are not unique unless the CLOSID is
    > also included. Bitmaps like rmid_busy_llc need to be sized by the
    > number of unique entries for this resource.
    >
    > Add helpers to encode/decode the CLOSID and RMID to an index. The
    > domain's busy_rmid_llc and the rmid_ptrs[] array are then sized by

    busy_rmid_llc -> rmid_busy_llc ?

    Could you please also mention the MBM state impacted?

    > index. On x86, this is always just the RMID. This gives resctrl a
    > unique value it can use to store monitor values, and allows MPAM to
    > decode the closid when reading the hardware counters.
    >
    > Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
    > Signed-off-by: James Morse <james.morse@arm.com>
    > ---
    > Changes since v1:
    > * Added X86_BAD_CLOSID macro to make it clear what this value means
    > * Added second WARN_ON() for closid checking, and made both _ONCE()
    > ---
    > arch/x86/include/asm/resctrl.h | 24 ++++++++
    > arch/x86/kernel/cpu/resctrl/internal.h | 2 +
    > arch/x86/kernel/cpu/resctrl/monitor.c | 79 +++++++++++++++++---------
    > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 7 ++-
    > 4 files changed, 82 insertions(+), 30 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
    > index 52788f79786f..44d568f3577c 100644
    > --- a/arch/x86/include/asm/resctrl.h
    > +++ b/arch/x86/include/asm/resctrl.h
    > @@ -7,6 +7,13 @@
    > #include <linux/sched.h>
    > #include <linux/jump_label.h>
    >
    > +/*
    > + * This value can never be a valid CLOSID, and is used when mapping a
    > + * (closid, rmid) pair to an index and back. On x86 only the RMID is
    > + * needed.
    > + */
    > +#define X86_RESCTRL_BAD_CLOSID ~0

    Should this be moved to previous patch where first usage of ~0 appears?

    Also, not having a size creates opportunity for inconsistencies. How
    about ((u32)~0) ?

    > +
    > /**
    > * struct resctrl_pqr_state - State cache for the PQR MSR
    > * @cur_rmid: The cached Resource Monitoring ID
    > @@ -94,6 +101,23 @@ static inline void resctrl_sched_in(void)
    > __resctrl_sched_in();
    > }
    >
    > +static inline u32 resctrl_arch_system_num_rmid_idx(void)
    > +{
    > + /* RMID are independent numbers for x86. num_rmid_idx==num_rmid */
    > + return boot_cpu_data.x86_cache_max_rmid + 1;
    > +}

    It seems that this helper and its subsequent usage eliminates the
    need for struct rdt_resource::num_rmid? Are any users left?

    Reinette

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